feat(library/style.md): add style guidelines draft
feat(library/standard/list): start on list library
feat(library/standard/equality_test.lean): add experiments with equality axioms

This reduces most of the current axioms for equality and heterogeneous equality to the basic rules for Id as an inductive type, plus Pi injectivity. There are universe problems that should go away in Lean 0.2.
feat(library/todo.md): add to do list
chore(library/standard/list): add copyright info to header
feat(library/standard/list): prove reverse reverse theorem
feat(library/standard): add natural number libraries using inductive types with add and mul
chore(.travis.yml): set up travis-ci for backup and diff notification
chore(library): add Makefiles to standard and hott libraries

Add simple 'Makefile' to compile '.lean' files into '.olean'
files. It assumes that 'lean' is in the 'PATH' variable. If this is
not the case, you can run 'make' while specifying the pathname for
'lean' as follows:

    $ make LEAN=~/work/lean0.1/build/shell/lean
chore(.travis.yml): compile .lean to .olean and upload to dropbox
feat(library/standard/kernel): copy kernel
feat(library/standard/nat): add le/lt
feat(library/standard/nat): use new kernel, change proofs to be compatible with the kenrel in this library, and prove some more theorems
chore(library/standard/Makefile): use -n and compile in right order
refactor(library/standard/kernel): change argument order for or_intro_left and or_intro_right
chore(library/standard): fix permission
chore(library/standard/Makefile): add and use extract_deps in Makefile
chore(library/standard/extract_dep): add EXCEPT to specify deps which do not need compilation
fix(library/standard/equality_test): add "import kernel"
fix(library/standard/list): use nat instead of Nat